Popliteal swellings are not uncommon. The majority are easily diagnosed on clinical examination alone. A sebaceous cyst will present as a firm swelling in the skin. It may be tender if it becomes inflamed and there may be a discharge from it. This presents as a soft lobulated swelling in the subcutaneous tissue. This presents as a soft swelling behind the knee, usually associated with varicose veins of the short saphenous system. Deeper lipomas are difficult to feel because of the tough overlying fascia. They do not always feel soft and lobulated, as superficial ones do. There may be several palpable lumps within the popliteal fossa. The patient will usually draw attention to a lesion distally, either on the leg or on the foot, usually on the lateral margin of the foot or the back of the leg. Other groups of nodes may be enlarged. The patient complains of a swelling behind the knee that interferes with knee movement, particularly flexion. A Baker’s cyst is a pulsion diverticulum of the knee joint caused by chronic disease within the joint. The patient will usually give a history of a painful knee joint and may have osteoarthritis or rheumatoid arthritis. Occasionally the cyst ruptures and the patient complains of severe pain in the calf, which has to be carefully distinguished from venous thrombosis.
Popliteal Swellings
Causes
History
Superficial
Sebaceous cyst
Lipoma
Varix of the short saphenous vein
Deep
Lipoma
Lymphadenopathy
Semi-membranosus bursa
Baker’s cyst
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Swellings
